Observing coronal nanoflares in active region moss

Abstract

The High-resolution Coronal Imager (Hi-C) has provided Fe XII 193A images of the upper transition region moss at an unprecedented spatial (~0.3-0.4 arcsec) and temporal (5.5s) resolution. The Hi-C observations show in some moss regions variability on timescales down to ~15s, significantly shorter than the minute scale variability typically found in previous observations of moss, therefore challenging the conclusion of moss being heated in a mostly steady manner. These rapid variability moss regions are located at the footpoints of bright hot coronal loops observed by SDO/AIA in the 94A channel, and by Hinode/XRT. The configuration of these loops is highly dynamic, and suggestive of slipping reconnection. We interpret these events as signatures of heating events associated with reconnection occurring in the overlying hot coronal loops, i.e., coronal nanoflares. We estimate the order of magnitude of the energy in these events to be of at least a few $10^{23}rg, also supporting the nanoflare scenario. These Hi-C observations suggest that future observations at comparable high spatial and temporal resolution, with more extensive temperature coverage are required to determine the exact characteristics of the heating mechanism(s).

Accepted for publication on The Astrophysical Journal Letters. 5 figures. Movies can be found at: http://www.lmsal.com/~ptesta/hic_moss/

References in corpus (5)

• Highly Efficient Modeling of Dynamic Coronal Loops
• Non-equilibrium of Ionization and the Detection of Hot Plasma in Nanoflare-heated Coronal Loops
• Hinode/Extreme-Ultraviolet Imaging Spectrometer Observations of the Temperature Structure of the Quiet Corona
• Observation and Modeling of Coronal "Moss" With the EUV Imaging Spectrometer on Hinode
• Estimating the Chromospheric Absorption of Transition Region Moss Emission

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